Mechanical performance after high-temperature exposure and Life Cycle Assessment (LCA) according to unit of stored energy of alternative mortars to Portland cement

Decoupling energy demand has led to the importance of energy storage for increasing the capacity of renewable energy power plants. In this field, Portland cement (PC) concrete is proving to be a promising way to store energy as it can be used as sensible thermal energy storage (TES) medium in concentrated solar power (CSP) technology. However, the high energy and water consumption involved in the PC manufacturing process makes it necessary to develop new alternatives. Thus, alkali-activated materials (AAM) and hybrid materials (HM) were manufactured using blast furnace slag and glass waste (GW) to replace the PC and the sand in concretes respectively in order to study their feasibility as TES media in parabolic through CSP systems. The viability of these proposed new systems was tested from a mechanical point of view, while taking into account the environmental aspect using Life Cycle Assessment (LCA) methodology to study carbon and water footprints. The new systems were exposed to high temperature (up to 500 °C), showing better performance than the ordinary PC under high temperatures, and their mechanical properties were not affected at all. After thermal treatment the alternatives show improvements of up to 79% compared to the PC reference sample. Furthermore, in terms of LCA analysis, it was concluded that TES systems with partial (HM) or total (AAM) substitution of PC by using by-products improve water use up to 40% when an AAM material includes GW as a recycled aggregate in its composition. Results likewise revealed a more than 100% reduction in the carbon footprint. These results open a new gate for the study of materials as TES since the alternatives to PC are more promising from an operational and environmental point of view.